1. Technical Field
The present invention relates to an electrostatic image forming apparatus and a process unit and a developing cartridge used for the image forming apparatus, e.g., in a copier, facsimile, laser printer, or other image forming apparatus.
2. Related Art
Conventionally, in image formation devices that supply developer to an electrostatic latent image formed on a photoreceptor and record the visible image showing the characters or images formed by transferring them onto a recording medium, processing units of the cartridge type are well known, in order to improve and simplify the maintenance characteristics and the changing operation.
With this sort of conventional image formation device, processing cartridges equipped with a developer receptacle and a processing roller that attaches to and detaches from the photoreceptor cartridge after mounting the photoreceptor cartridge in the body of the image-formation device are well known. Additionally, processing units having a processing cartridge mounted on the photoreceptor cartridge in advance are known in which the processing unit is configured so that it can be attached to and detached from the body of the image formation device.
However, with the conventional image formation devices described above, the system is configured so that the photoreceptor cartridge is positioned relative to the image formation device, and furthermore, the processing cartridge is positioned relative to the photoreceptor cartridge. In other words, the processing cartridge is positioned relative to the image formation device via the photoreceptor cartridge. An explanation shall be given regarding this using FIG. 9.
FIG. 9 is a drawing showing the state where a processing unit 4 composed of a processing cartridge 36 and a photoreceptor cartridge 35 is mounted in a conventional image formation device as described above. First, regarding the photoreceptor cartridge 35, by maintaining the drum axis 37a of this photoreceptor cartridge 35 at a specified location in the image formation device, and also, by joining the protrusion 305 of the photoreceptor cartridge 35 and the body side positioning component 300 that is located in the image formation device, the photoreceptor cartridge 35 is positioned relative to the image formation device. In addition, by maintaining the processing roller axis 40a of the processing cartridge 36 at a specified location in the photoreceptor cartridge 35, and also, by joining the operating component 315 of the processing cartridge 36 and the photoreceptor side positioning component 310 that is located in the photoreceptor cartridge 35, the processing cartridge 36 is positioned relative to the photoreceptor cartridge 35. In other words, as stated previously, the processing cartridge 36 is positioned relative to the image formation device via the photoreceptor cartridge 35.
For this reason, the amount of displacement of the processing cartridge relative to the image formation device is an amount derived by adding the amount of displacement of the photoreceptor cartridge relative to the image formation device and the amount of displacement of the processing cartridge relative to the photoreceptor cartridge. Therefore, the possibility has existed that the amount of displacement of the processing cartridge relative to the image formation device would increase, or in other words, that positioning precision of the processing cartridge relative to the image formation device would worsen.
Also, as the positioning precision of the processing cartridge relative to the image formation device worsens, the printing paper transport pathway space composed of the processing cartridge and body of the image formation device can become disrupted. When the transport pathway space becomes disrupted, printing paper is no longer transported smoothly, and errors are likely to occur such as the printing paper jamming while being transported.